Three cases of methylmercury intoxication which eluded correct diagnosis.

Three casual workers engaged in the production of mercuric acetate were admitted to hospital within 22 calendar days of each other, respectively 30,48 and 5 days after their last working day.

The workers served the same reactor in which elemental mercury was oxidized by peroxide and mercuric acetate was formed by the reaction of mercuric oxide with acetic acid.

The diagnosis of mercury vapour intoxication of the first two patients was made 21 and 16 days after their admission when the third patient was admitted and hospitals were informed about their exposure.

This diagnosis was made without considering :

(a) that the observed signs were characteristic of methylmercury intoxication and are rarely present in mercury vapour intoxication ;

(b) the degree of deterioration after removal from exposure implicated methylmercury ;

(c) that blood mercury concentrations extrapolated to the last day at work were in the range, which had been associated with severe intoxication in the Iraq methylmercury epidemic ;

(d) at the time of the first blood mercury estimations the blood urinary mercury concentration ratios were 11.2,5.4 and 2.4 while this ratio is below 0.5 in mercury vapour intoxication or in workers exposed to mercury vapour.